After the hydraulic test is completed, the fully automatic heat exchanger unit sometimes needs to undergo an air tightness test.That is, use air and soapy water or side leakage gas for detection.The airtightness test plays an important role in the sealing detection of heat exchange tubes and the compression welding of heat exchange tubes.The testing standards are as follows:
The air tightness test standard of the fully automatic heat exchanger unit involves many aspects, including test pressure,Pressure holding time, pressure drop requirements and testing methods, etc. The relevant standards mainly include GB/T 29466-2023 "Plate Heat Exchanger Unit", etc.
The following are the specific contents: Test pressure: Different testing standards and testing methods have different requirements for test pressure. Generally speaking, the airtightness test pressure is equal to the design pressure.
Generally speaking, the air tightness test pressure is equal to the design pressure. For example, according to GB/T 29466-2023, the hydraulic test pressure of the plate heat exchanger unit is 1.5 times the design pressure (minimum ≥ 0.6MPa).The air tightness test pressure is usually equal to the design pressure.In addition, in some air pressure tests, the test pressure is about 1.15 times the design pressure.
Dwell time: Dwell time is key to ensuring leaks can be adequately detected.Dwell time is critical to ensure leaks can be adequately detected.It is usually required that the pressure stabilization time be no less than 30 minutes after reaching the design pressure.If an air pressure test is used, after reaching the test pressure, close the air inlet valve and start the pressure stabilization phase. The pressure stabilization time is generally not less than 30 minutes. Observe whether the pressure gauge reading has dropped.
Pressure drop requirement: Pressure drop is one of the important indicators to judge whether the air tightness is qualified.According to GB/T 29466-2023, the pressure drop during hydraulic testing should be ≤1% of the test pressure.In air pressure tests, it is usually stipulated that if the pressure drop is within the range of 1% - 3% of the test pressure, the air tightness is preliminarily considered to be good.
Testing methods and qualification determination:The commonly used detection method is to apply soapy water or other leak detection liquid to the welds, flange connections, sealing gaskets and other possible leaking parts of the heat exchanger.If bubbles are generated, it means there is a leak in that part. If the pressure drop meets the requirements during the pressure holding time and no bubbles are generated when testing with leak detection fluid, the air tightness test is passed.
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